Congratulations on your new 2026 Kia Sportage! That's a great vehicle. I can understand why you're perplexed by this. It's not normal for a brand new car to behave like that, and it's frustrating when you don't get any warning lights. You're not the only one to have this kind of problem. While it's not a widespread issue, it can happen. The fact that the car cranked longer and had a lack of power is a strong indicator of a fuel issue. Your theory about water in the gas is a very good one. The fuel system in modern cars is very sensitive to contaminants, and even a small amount of water in the fuel can cause a lot of problems.
The longer crank time is a sign that the engine is not getting the correct air/fuel mixture, and the lack of power is a sign that the engine is not getting enough fuel. The fact that it went away after you put more gas in the tank is a huge clue. A few other things could have caused this. It could have been an intermittent software glitch in the engine's computer. It could have also been a bad sensor, like a fuel pressure sensor, that was not working correctly. However, the fact that you didn't get a warning light or a code makes it less likely. An intermittent problem can be too short for the computer to register a fault.
My best advice is to just monitor the situation. Keep the gas tank full for a while, and see if the problem comes back. If it does, you should take it to a dealership immediately. Since it's a brand new car, you should not be having these kinds of problems, and it would be a good idea to have it looked at.
